Lubricating grease composition

ABSTRACT

The present invention relates to lubricating grease compositions comprising (a) at least one high-viscosity fluorinated oil having a viscosity of 500 to 1500 mm2/s, (b) boron nitride and (c) a binder selected from bentonite, alkali metal phosphates, aluminum phosphates, alkali metal silicates, alkaline earth metal silicates, aluminum silicates, alkaline earth metal carbonates, calcium borate, silicon dioxide, titanium dioxide, aluminum oxide and mixtures thereof. The lubricating grease compositions find use especially in the high-temperature sector, for example for the lubrication of oven pullout rails.

The present invention relates to lubricating grease compositions thatare especially suitable as high-temperature lubricating greases and finduse for lubrication in oven systems, driers, dishwashers, electricmotors or ventilators.

Lubricating greases generally comprise a thickener dissolved ordispersed in a base oil, and dispersants are frequently employed forbetter and more stable distribution of the thickener. The thickenerserves to establish the desired consistency, and a multitude ofinorganic and organic compounds are used.

Base oils used are mineral oils and synthetic oils. Frequently,perfluorinated polyalkyl ethers (PFPEs) are used, i.e. fluorinatedsynthetic oils having good lubrication properties that are chemicallyunreactive and stable at high temperature and therefore nontoxic (see,for example, “Synthetics, Mineral Oils and Bio-Based Lubricants”, LeslieR. Rudnick ed., Taylor & Francis, CRC Press, 2006). For instance, WO97/47710 describes lubricating grease compositions comprising, as baseoil, a mixture of a hydrocarbon oil and a perfluorinated polyalkyl etheroil (PFPE) and a thickener based on a diurea compound. The compositionmay also comprise polytetrafluoroethylene (PTFE) and customaryadditives.

EP 657 524 describes lubricating grease compositions comprising amineral oil and/or a synthetic oil on a hydrogenated basis, aperfluorinated polyalkyl ether oil and PTFE as thickener.

DE 10 2004 021 812 A1 describes a lubricating grease comprising a baseoil, a thickener, especially a polyurea, and an inorganic materialdistributed in the lubricating grease, such as silicon dioxide.

WO 2008/154997 A1 describes a lubricating grease comprising a base oil,an ionic liquid, a thickener and an additive. The ionic liquid is saidto bring about an increase in the lifetime and lubricity of thelubricant and to serve to adjust the viscosity and the electricalconductivity.

Within the higher temperature range (200° C. to more than 600° C.), manyof the known lubricants, for example, polyfluorinated compounds, meetthe limits of material durability and are therefore no longer usable inspite of excellent sliding and lubricating properties within the highertemperature range.

WO 2013/037456 therefore describes high-temperature greases comprising afluorine-free base oil, a thickener that may be PTFE, additives andoptionally a further fluorine-free oil component.

EP 1589291 A1 discloses an oven pullout guide having rolling bodiesarranged in a rolling body cage. The rolling body cage and the rollingbodies here have a lubrication layer which comprises a solid lubricant,for example graphite, molybdenum sulfide, tungsten disulfide or boronnitride, and is applied and baked in the form of a paint.

WO 2010/046456 A1 describes a pullout guide for a baking oven in whichthe tracks of the pullout guide have been lubricated with boron nitrideand/or a polysiloxane-containing lubricant.

EP 648 832 A1 describes lubricating grease compositions comprising afluorinated polymer oil, boron nitride and optionally solid fluorinatedpolymers. The lubricating grease compositions are said to have goodlubricating properties even under harsh operating conditions.

US 2008/0167208 describes lubricating grease compositions comprising aperfluoropolyether oil having a kinematic viscosity of 50-1500 mm²/s at40° C., optionally a thickener and further customary additives. Thelubricating grease compositions are said to be usable at highertemperatures in contact with graphite or molybdenum disulfide as well.

PTFE-containing lubricating greases form toxic vapors at relatively hightemperatures and are additionally washed out relatively quickly incleaning operations by water. PTFE-free lubricating greases in turn havethe disadvantage that they are washed out even more quickly by waterthan PTFE-containing lubricating greases.

It is therefore an object of the present invention to providelubricating grease compositions having improved ease of washout bywater. Moreover, the lubricating grease compositions are to haveimproved thermal stability and bring about a longer lifetime of thelubrication at high temperatures.

This object is achieved by a lubricating grease composition comprisingat least one high-viscosity, fluorinated oil, hexagonal boron nitrideand a binder.

The present invention therefore relates to a lubricating greasecomposition comprising

-   -   (a) at least one fluorinated oil having a viscosity of 500 to        1500 mm²/s, preferably 500 to 1100 mm²/s;    -   (b) boron nitride and    -   (c) a binder.

The kinematic viscosity is measured with a SVM 300 viscometer, AntonPaar, at a temperature of 40° C.

In one embodiment, component (a) comprises fluorinated, especiallyperfluorinated, polyalkyl ether oils or fluorinated silicone oils,especially perfluorinated silicone oils, and mixtures thereof.

Suitable perfluorinated polyalkyl ether oils are described, for example,in WO 97/47710 or EP 657 524, which are fully incorporated by reference.

In one embodiment, the perfluorinated polyalkyl ether oils conform tothe formula:

A¹-[OCF₂]_(a)—[OC₂F₄]_(b)—[OC₃F₆]_(c)—[OC₄F₈]_(d)—[OCF₂CF(CF₃)]_(e)—[OCF(CF₃)CF₂]_(f)-A²

in which

A¹ is —CF₃, —C₂F₅, or —C₃F₇;

A² is —OCF₃, —OC₂F₅, or —OC₃F₇;

a, b, c, d, e and f are randomly distributed and are 0 or an integerfrom 1 to 200, where not all of them can simultaneously be 0.

In a further embodiment, e/a and f/a are in the range from 20 to 50 andb/a is in the range from 0.5 to 2.

In a further embodiment, c and d are 0. More preferably, theperfluorinated polyalkyl ethers are formed from the following units:

—[OCF₂CF(CF₃)]_(e) or

—[OCF₂]_(a)—[OC₂F₄]_(b) or

—[OCF₂]_(a)—[OCF₂CF(CF₃)]_(e)

where e/a is in the range from 20 to 50 and b/a in the range from 0.5 to2.

In a further embodiment, the perfluorinated polyalkyl ether oils conformto the formula:

CF₃—[OCF(CF₃)CF₂]_(f)—[OCF₂]_(a)—[OCF₂CF(CF₃)]_(e)—OCF₃

In which a, e and f are randomly distributed and are 0 or an integerfrom 1 to 200, where not all of them can simultaneously be 0, and e/aand f/a are in the range from 20 to 50.

In a further embodiment, the perfluorinated polyalkyl ether oils conformto the formula:

T-O-[A-B]_(z)-[A-B′]_(z′)-A-T′  (I)

-   -   in which:

-A=-(X)_(a)—O-A′-(X′)_(b)—

in which A′ is a perfluoropolyether chain comprising one or more repeatunits selected from (CF₂O), (CF₂CF₂O), (CF₂CF₂CF₂O) and (CF₂CF₂CF₂CF₂O)and optionally (CF(CF₃)O)—, (CF(CF₃)CF₂O)—, (CF₂CF(CF₃)O)— units;

X and X′ are the same or different and are —CF₂—, —CF₂CF₂— or optionally—CF(CF₃)—;

a and b are the same or different and are integers having a value of 0or 1, with the proviso that the index a in the A block bonded to the endgroup T-O— is 1 and the index b in the A block bonded to the end groupT′ is 0;

-   -   B is a block composed of units which derive from one or more        olefins of the formula (Ia), at least one of which is        free-radically homopolymerizable,

—[(CR₁R₂—CR₃R₄)_(j)(CR₅R₆—CR₇R₈)_(j′)]—  (Ia)

in which

j is an integer from 1 to 5,

j′ is an integer from 0 to 4, with the proviso that (j+j′) is greaterthan 2 and less than 5;

R₁, R₂, R₃, R₄, R₅, R₆, R₇ and R₈ are the same or different and areselected from halogen; H;

-   -   C₁-C₆-(per)haloalkyl, where halogen is F and/or Cl; C₁-C₆-alkyl        which optionally contains heteroatoms; and        C₁-C₆-oxy(per)fluoroalkyl;

z is an integer of not less than 2;

z′ is 0 or an integer;

where z and z′ have such a value that the number-average molecularweight of the polymer of the formula (I) is in the range of 500-500 000;

B′ is a block which derives from one or more olefins of the formula(Ia), but at least one of the substituents R₁ to R₈ is different than inblock B, where (j+j′) is not less than 2 and less than 5;

the end groups T and T′ are the same or different and are perfluoroalkylgroups having 1 to 3 carbon atoms, where a fluorine atom may be replacedby a chlorine or hydrogen atom; or nonfluorinated C₁-C₆-alkyl groups.

These polyethers oils are described in EP 2 089 443, and reference ismade in full to the disclosure thereof, especially the embodimentsdisclosed in the claims.

In one embodiment, component (a) may additionally comprise anonfluorinated oil, especially a mineral oil. The nonfluorinated oil isgenerally present in an amount of 0.1% to 40% by weight, especially 0.5%to 30% by weight, based on the amount of the fluorinated oil.

The lubricating grease composition further comprises boron nitride,especially hexagonal boron nitride. In one embodiment, the lubricatinggrease composition comprises hexagonal α-boron nitride. In a furtherembodiment, the boron nitride has a BET surface area in the range from10 to 20 m²/g, determined according to ISO 9277:2010. In a furtherembodiment, the boron nitride has a median particle size D50 of 1 to 10μm, especially 2 to 6 μm, determined by means of laser diffractometry(Malvern Mastersizer 3000). A suitable boron nitride is available, forexample, under the Boronid® trade name from ESK Ceramics GmbH & Co. KG,Germany.

The lubricating grease composition further comprises a binder. Thebinder generally has a median particle size D50 in the range from 1 to10 μm, preferably 2 to 8 μm, determined by means of laserdiffractometry.

In one embodiment, the binder is selected from bentonite, alkali metalphosphates, aluminum phosphates, alkali metal silicates, alkaline earthmetal silicates, aluminum silicates, alkaline earth metal carbonates,calcium borate, silicon dioxide, titanium dioxide, aluminum oxide andmixtures thereof. Preference is given to bentonite, alkali metalphosphates, aluminum phosphates and mixtures thereof. More preferably,the binder is organically modified bentonite or a mixture of organicallymodified bentonite with at least one further binder selected from alkalimetal phosphates, aluminum phosphates, alkali metal silicates, alkalineearth metal silicates, aluminum silicates, alkaline earth metalcarbonates, silicon dioxide, titanium dioxide, aluminum oxide andmixtures thereof. The further binder is generally present in an amountof 0.1% to 50% by weight, especially 0.5% to 40% by weight, based on theamount of the organically modified bentonite.

Preferred silicon dioxide is organically modified fumed silica, andpreferred titanium dioxide is organically modified pyrogenic titaniumdioxide. Modified fumed silica and modified pyrogenic titanium dioxideare products that have been surface-treated with an organosilane,especially with an alkylsilane. Corresponding products, such as AerosilR 912, Aerosil R 812, Aerosil R 805, Aerosil R 202, Aeroxide® TiO₂ T805, Aeroxide® TiO₂ NKT 90, VP NKT 65, are commercially available, forexample from Evonik Industries AG, Germany or Wacker Chemie AG, Germany.

Bentonite is a mixture of various clay minerals with montmorillonite(60% to 80%) as the most important constituent. Further accompanyingminerals are quartz, mica, feldspar, pyrite or else calcite. Theexpression “bentonite” encompasses all naturally occurring versions andmodified bentonites. Bentonite is commercially available in the form ofvarious commercial products. In the context of the present invention,preference is given to using organically modified, especiallyhydrophobically modified, bentonite, for example the commercial productBARAGEL® from Elementis Specialities Inc., USA.

Organically hydrophobically modified bentonite can be obtained, forexample, by the reaction of natural or purified bentonite withquaternary ammonium compounds in the manner of a cation exchangereaction in which, for example, alkali metal cations are exchanged forquaternary ammonium compounds. Quaternary ammonium compounds suitablefor this reaction are, for example, those of the general formulaR¹R²R³R⁴N⁺X⁻ where X is an equivalent of an anion, for example sulfate,hydrogensulfate, alkylsulfate, arylsulfate, alkylsulfonate,arylsulfonate, halide, phosphate, carbonate, alkylphosphate,alkylcarbonate, nitride, alkoxide, hydroxide, tetrafluoroborate orperchlorate, especially halide, and R¹, R², R³ or R⁴ may be the same ordifferent and may be C₁-C₂₀-alkyl. For example, R¹ and R² may be thesame or different and may be C₁-C₄-alkyl, and R₃ and R₄ may be the sameor different and may be C₁₂-C₂₀-alkyl. More particularly, it is possibleto use quaternary ammonium salts in which X is halide, especiallychloride, R′ and R² are methyl and R₃ and R₄ are the same or differentand are C₁₆-C₁₈-alkyl. The commercial product BARAGEL© is bentonitemodified with Me₂N(C₁₆-C₁₈-alkyl)₂Cl.

When bentonite is used as binder, the lubricating grease composition, ina preferred embodiment, additionally comprises water in an amount of0.01% to 1% by weight, especially 0.05% to 0.2% by weight, based on thetotal mass of the composition. Water serves here as an activating agentfor bentonite, especially for activation of the dispersing andthickening properties of bentonite.

In a further embodiment, the lubricating grease composition of theinvention may comprise at least one additive, especially an additivecustomary in the field of lubricating grease compositions. The additiveis preferably selected from antioxidants, for example functionalizedperfluoropolyalkyl ethers as described in EP 1 354 932 A1 and U.S. Pat.No. 5,550,277; antiwear additives, for example functionalizedperfluoropolyalkyl ethers as described in WO 2016/020232;anticorrosives, for example sodium sebacate, functionalizedperfluoropolyalkyl ethers as described in U.S. Pat. No. 5,550,277; dyes,for example azo dyes, and solid lubricants, for example molybdenumdisulfide, tungsten disulfide, tin sulfide.

In a further embodiment, the lubricating grease composition of theinvention comprises

(a) 50-96% by weight of the fluorinated oil;

(b) 0.9-20% by weight of boron nitride; and

(c) 3-25% by weight of the binder;

(d) 0-5% by weight, especially 0.01-5% by weight, of at least oneadditive;

based in each case on the total weight of the composition.

In a further embodiment, the lubricating grease composition of theinvention comprises

(a) 50-96% by weight of at least one perfluorinated polyalkyl ether oil;

(b) 0.9-20% by weight of boron nitride; and

(c) 3-25% by weight of organically modified bentonite;

(d) 0-5% by weight, especially 0.1-5% by weight, of at least oneadditive;

based in each case on the total weight of the composition.

In one embodiment, the lubricant composition is essentially free ofPTFE.

In a further embodiment, the lubricating grease composition isessentially free of an ionic liquid.

In a further embodiment, the lubricating grease composition isessentially free of graphite.

“Essentially free” means that the lubricating grease compositioncontains less than 0.5% by weight of PTFE, less than 0.5% by weight ofionic liquid or less than 0.5% by weight of graphite, especially 0% byweight of each of these components, based on the total mass of thecomposition.

The lubricating grease composition of the invention is generallyproduced by mixing the components under high shear force, for exampleusing a rotor-stator mixer, optionally followed by a homogenization, forexample using a roll mill.

It has been found that, surprisingly, the lubricating greasecompositions of the invention have a number of advantageous propertiescompared to known lubricating greases:

-   -   very good compatibility of all components    -   better adhesion on metal surfaces    -   longer lifetime at high operating temperature    -   lower ease of washout by water; this results in the possibility        of repeated machine cleaning of lubricated metal parts, for        example of pullout rails of baking ovens in machine dishwashers,        without impairment of the function of the metal parts    -   no formation of possibly toxic breakdown products in the case of        heating above 100° C.    -   better high-temperature properties    -   additional lubricity by virtue of the oil component compared to        pulverulent products.

The lubricating grease compositions of the invention are suitable forlubrication within the temperature range from −30° C. to 700° C.,especially +20 to 300° C. They can therefore be used in many fields. Forinstance, they are usable for the lubrication of sliding guides andrunning wheels in oven systems or roller bearings and slide bearings indriers, electric motors or ventilators, for the lubrication of molds,especially molds for the injection molding of plastics, machines andinstallations, especially for the food and animal feed industry.Examples of applications are the lubrication of: roller bearings andslide bearings, sliding guides, valves, joints, slides, pillar guides,ejectors and other sliding surfaces as, for example, in circularconveyor systems, painting lines, calenders, kiln cars, ventilators,switches, film stretching systems, extraction systems, textilemachinery, wood press systems, pumps, driers, motors, tire molds,construction machinery, electrical engineering and automobiletechnology, elastomer and plastics technology, and applications in thecorrugated cardboard industry, paper industry and steel industry, andmachinery and installations, for example, in the food and animal feedindustry.

Preferably, the lubricating grease composition of the invention is usedfor the lubrication of sliding guides and running wheels in oven systemsor roller bearings and slide bearings in driers, electric motors orventilators. Especially preferred is the use of the lubricating greasecompositions of the invention for the lubrication of oven pullout rails.

The lubricating grease composition is applied by application to theparts to be lubricated in an amount suitable for lubrication. Preferenceis given to applying the lubricating grease composition of the inventionas a paste. This form of application enables very exact selection andcoating of the application areas. The lubricating grease composition canbe applied in a simple manner without the lubricating grease compositionflowing away or dripping off, for example, at the ends of the tracks ofoven pullout rails.

An optional aftertreatment by slide grinding after the application ofthe lubricating grease composition enables better distribution andadhesion of the lubricating grease on a metallic substrate, for example.

Preferably, the lubricant composition is thixotropic, meaning that theviscosity decreases under mechanical action and the original viscosityis re-established after the shear stress has ended. As a result, thepastes can be distributed relatively easily on the surface of ovenpullout rails, for example, under pressure without dripping off.

The examples which follow elucidate the invention without restrictingit.

EXAMPLE 1

Two perfluorinated polyether oils (68% by weight of PFPE oil 1, 500 cStat 40° C. from DuPont, USA and 10% by weight of PFPE oil 2, 1005 cSt at40° C. from DuPont, USA) were introduced into a mixing vessel and heatedto 100° C. while stirring for 15 min. Thereafter, BARAGEL® (14.9% byweight, organically hydrophobically modified bentonite from ElementisSpecialties Inc., USA) were introduced into the mixing vessel, theheating was switched off and the resulting mixture was stirred for fiveminutes. Then 0.1% by weight of water was added and the mixture wasstirred for 30 min. After cooling to room temperature, boron nitride (5%by weight Boronid®, ESK Ceramics GmbH & Co. KG, Germany) and ananticorrosive (2% by weight, Irgacor®, BASF SE, Germany) were introducedinto the mixing vessel and the resulting mixture was stirred for 30 min.The resulting lubricant grease was homogenized with a roll mill. Thefigures in % by weight are each based on the total weight of thelubricant grease.

Test Program and Results

The lubricating grease composition produced according to example 1 wasfirst subjected to a VKA test (four-ball apparatus, ASTM D1831/DIN51350-4). The VKA welding force was determined as 4800 N and the VKAwear as 0.9 mm under a load of 150 kg/1 min.

For the lubricating grease composition produced according to example 1,the thermal stability was also determined at 300° C. A measure employedfor the thermal stability was the evaporation rate with time:

Hours: 0 24 72 140

Evaporation rate [%]: 0 14 26 41

In addition, the following were determined for the lubricating greasecomposition produced according to example 1:

-   -   steel corrosion (Emcor) in distilled water (ISO 11007): grade        1/1    -   base oil viscosity at 40° C. (DIN 51562): 575 mm²/s and    -   NLGI consistency class (DIN 51818): NLGI 1.

Washout Tests

Washout tests were conducted for the lubricating grease compositionproduced according to example 1 and three comparative samples(comparative example 1, comparative example 2, comparative example 3).For this purpose, the various samples were applied to oven pullout railsand subjected to the following cycle: the oven pullout rails weresubjected to a temperature of 250° C. in an oven for 4 h; thereafter,the rails were taken out of the oven and treated with a commercialdishwashing composition in a machine dishwasher at 70° C. for 2 h; afterthe wash cycle, the rails were taken out of the machine dishwasher anddried at 105° C. for 1 h. (3 cycles were conducted for each sample; therails were thus in the oven for a total of 12 h and in the dishwasherfor 6 h.) Composition of the comparative examples (% by weight, based onthe total weight of the composition):

COMPARATIVE EXAMPLE 1

74.75% PFPE (perfluorinated polyether; 500 mm²/s)

25% PTFE (polytetrafluoroethylene)

0.25% anticorrosive

COMPARATIVE EXAMPLE 2

81% PFPE (500 mm²/s)

10% PFPE (1005 mm²/s)

5% PTFE

2% SiO2

2% anticorrosive

COMPARATIVE EXAMPLE 3

10% PFPE (1005 mm²/s)

83% PFPE (500 mm²/s)

5% boron nitride

1% graphite

1% WS₂ (tungsten sulfide)

The following results were obtained:

-   Example 1: weight loss after the third wash cycle: <50%; rail has    good mobility.-   Comparative example 1: weight loss after the third wash cycle: 75%-   Comparative example 2: weight loss after the third wash cycle: 50%-   Comparative example 3: weight loss after the third wash cycle: 60%-   Comparative example 2, which contains PTFE, evolves toxic, vaporous    breakdown products and is therefore unsuitable for use in baking    ovens in spite of good washout results.

Endurance Tests

Endurance tests were conducted for the lubricating grease compositionproduced according to example 1 and two comparative samples (comparativeexamples 4 and 5). For this purpose, the various samples were applied tooven pullout rails and the pullout rails were mounted on side grids.Subsequently, the grids were installed into a baking oven. A test loadwas positioned in the middle of a baking sheet in the oven. The weightedbaking sheet was pulled in and out using a pneumatic cylinder. The railswere subjected to an endurance test with 24 000 cycles. After every 6000cycles, movement force and lowering of the rails were tested and,likewise after every 6000 cycles, the rails were subjected to a machinedishwasher wash cycle. After a total of 24 000 cycles, the rails weredeinstalled and examined. The testing was conducted with the followingparameters and according to the following schematic procedure:

Test Cycles: 24 000 parameters: Additional load: 7.5 kg Temperature:250° C. Speed: 10 cycles/min Level: middle level in the baking ovenPullout: restriction by 20 mm in both directions Test 1. Installation ofthe rails procedure: 2. Application of the test load in the middle ofthe baking sheet 3. Endurance test for 24 000 cycles 4. Determination ofthe movement force and lowering after every 6000 cycles 5. Machinedishwasher cycle after every 6000 cycles 6. Deinstallation andexamination of the rails 7. Evaluation

Composition of the comparative examples (% by weight, based on the totalweight of the composition):

COMPARATIVE EXAMPLE 4

as comparative example 2, see above.

COMPARATIVE EXAMPLE 5

90.5% PFPE (500 mm²/s)

6% boron nitride

3.25% SiO₂

0.25% anticorrosive

The following results were obtained:

-   Example 1: The sample passed the test (5 wash cycles, good running    properties up to 18 000 cycles, continuing with somewhat poorer    running properties up to 24 000 cycles).-   Comparative example 4: The sample passed the test (5 wash cycles,    good running properties up to 18 000 cycles, continuing with poorer    running properties up to 24 000). However, the composition evolved    toxic breakdown products at temperatures above 250° C.-   Comparative example 5: The sample failed the test (failed after 12    000 cycles, ball bearings jammed owing to lack of lubrication).

1. A lubricating grease composition comprising (a) at least onefluorinated oil having a viscosity of 500 to 1500 mm²/s at 40° C.; (b)boron nitride and (c) at least one binder selected from bentonite,alkali metal phosphates, aluminum phosphates, alkali metal silicates,alkaline earth metal silicates, aluminum silicates, alkaline earth metalcarbonates, calcium borate, silicon dioxide, titanium dioxide, aluminumoxide and mixtures thereof.
 2. The lubricating grease composition asclaimed in claim 1, comprising, based in each case on the total weightof the composition, (a) 50-96% by weight of the fluorinated oil; (b)0.9-20% by weight of boron nitride; and (c) 3-25% by weight of thebinder.
 3. The lubricating grease composition as claimed in claim 1 or2, wherein the fluorinated oil has with a viscosity of 500 to 1100 mm²/sat 40° C.
 4. The lubricating grease composition as claimed in any of thepreceding claims, wherein the fluorinated oil is selected fromperfluorinated polyalkyl ether oils, perfluorinated silicone oils andmixtures thereof, and is especially selected from perfluorinatedpolyalkyl ether oils and mixtures thereof.
 5. The lubricating greasecomposition as claimed in any of the preceding claims, wherein thebinder is selected from bentonite, fumed silica (SiO₂), talc (magnesiumsilicate hydrate), calcium carbonate, calcium borate, pyrogenic titaniumdioxide, aluminum oxide and mixtures thereof.
 6. The lubricating greasecomposition as claimed in any of the preceding claims, wherein thebinder is organically modified bentonite or a mixture of organicallymodified bentonite with at least one further binder selected from alkalimetal phosphates, aluminum phosphates, alkali metal silicates, alkalineearth metal silicates, aluminum silicates, alkaline earth metalcarbonates, silicon dioxide, titanium dioxide, aluminum oxide andmixtures thereof.
 7. The lubricating grease composition as claimed inany of the preceding claims, wherein the boron nitride is hexagonalboron nitride, especially hexagonal α-boron nitride.
 8. The lubricatinggrease composition as claimed in any of the preceding claims, comprisingessentially no PTFE.
 9. The lubricating grease composition as claimed inany of the preceding claims, comprising essentially no ionic liquid. 10.The lubricating grease composition as claimed in any of the precedingclaims, comprising essentially no graphite.
 11. The lubricating greasecomposition as claimed in any of the preceding claims, additionallycomprising at least one nonfluorinated oil.
 12. The lubricating greasecomposition as claimed in any of the preceding claims, additionallycomprising 0.01% to 1% by weight of water, based on the total weight ofthe composition.
 13. The lubricating grease composition as claimed inany of the preceding claims, additionally comprising at least oneadditive.
 14. The lubricating grease composition as claimed in claim 13,wherein the additive is selected from antioxidants, viscosity indeximprovers, pour point depressants, antiwear additives, anticorrosives,rust preventers, dyes, and solid lubricants.
 15. The lubricating greasecomposition as claimed in claim 14, comprising 0.05-5% by weight of atleast one additive.
 16. The use of a lubricating grease composition asclaimed any of claims 1 to 15 for lubrication within the temperaturerange from −30° C. to 700° C., especially +100° C. to 310° C.
 17. Theuse of a lubricating grease composition as claimed in any of claims 1 to15 for the lubrication of sliding guides and running wheels in ovensystems or roller and slide bearings in driers, electric motors orventilators, for the lubrication of molds, especially molds for theinjection molding of plastics, machines and installations, especiallyfor the food and animal feed industry.
 18. A lubricating method whereina lubricating grease composition as claimed in any of claims 1 to 15 isapplied to the parts to be lubricated.
 19. The lubricating method asclaimed in claim 18, wherein the lubricating grease composition isapplied within the temperature range from −30° C. to 700° C., especially+100° C. to 310° C.
 20. The lubricating method as claimed in claim 18 or19 for lubrication of sliding guides and running wheels in oven systemsor roller and slide bearings in driers, electric motors or ventilators,for lubrication of molds, especially molds for the injection molding ofplastics, machines and installations, especially for the food and animalfeed industry.